The NSA geolocation system used by JSOC is known by the code name GILGAMESH. Under the program, a specially constructed device is attached to the drone. As the drone circles, the device locates the SIM card or handset that the military believes is used by the target.

Relying on this method, says the former JSOC drone operator, means that the “wrong people” could be killed due to metadata errors, particularly in Yemen, Pakistan and Somalia. “We don’t have people on the ground – we don’t have the same forces, informants, or information coming in from those areas – as we do where we have a strong foothold, like we do in Afghanistan. I would say that it’s even more likely that mistakes are made in places such as Yemen or Somalia, and especially Pakistan.”

Every cell-phone network knows the approximate location of all phones capable of receiving calls. This is necessary to make the system work; if the system doesn’t know what cell you’re in, it isn’t able to route calls to your phone. We already know that the NSA conducts physical surveillance on a massive scale using this technique.

By triangulating location information from different cell phone towers, cell phone providers can geolocate phones more accurately. This is often done to direct emergency services to a particular person, such as someone who has made a 911 call. The NSA can get this data either by network eavesdropping with the cooperation of the carrier, or by intercepting communications between the cell phones and the towers. A previously released a Top Secret NSA document says this: “GSM Cell Towers can be used as a physical-geolocation point in relation to a GSM handset of interest.”

According to a former drone operator for the military’s Joint Special Operations Command (JSOC) who also worked with the NSA, the agency often identifies targets based on controversial metadata analysis and cell-phone tracking technologies. Rather than confirming a target’s identity with operatives or informants on the ground, the CIA or the U.S. military then orders a strike based on the activity and location of the mobile phone a person is believed to be using.

The drone operator, who agreed to discuss the top-secret programs on the condition of anonymity, was a member of JSOC’s High Value Targeting task force, which is charged with identifying, capturing or killing terrorist suspects in Yemen, Somalia, Afghanistan and elsewhere.

His account is bolstered by top-secret NSA documents previously provided by whistleblower Edward Snowden. It is also supported by a former drone sensor operator with the U.S. Air Force, Brandon Bryant, who has become an outspoken critic of the lethal operations in which he was directly involved in Iraq, Afghanistan and Yemen.

In one tactic, the NSA “geolocates” the SIM card or handset of a suspected terrorist’s mobile phone, enabling the CIA and U.S. military to conduct night raids and drone strikes to kill or capture the individual in possession of the device.

The agency also equips drones and other aircraft with devices known as “virtual base-tower transceivers”—creating, in effect, a fake cell phone tower that can force a targeted person’s device to lock onto the NSA’s receiver without their knowledge.

The former JSOC drone operator is adamant that the technology has been responsible for taking out terrorists and networks of people facilitating improvised explosive device attacks against U.S. forces in Afghanistan. But he also states that innocent people have “absolutely” been killed as a result of the NSA’s increasing reliance on the surveillance tactic.

One problem, he explains, is that targets are increasingly aware of the NSA’s reliance on geolocating, and have moved to thwart the tactic. Some have as many as 16 different SIM cards associated with their identity within the High Value Target system. Others, unaware that their mobile phone is being targeted, lend their phone, with the SIM card in it, to friends, children, spouses and family members.

Some top Taliban leaders, knowing of the NSA’s targeting method, have purposely and randomly distributed SIM cards among their units in order to elude their trackers. “They would do things like go to meetings, take all their SIM cards out, put them in a bag, mix them up, and everybody gets a different SIM card when they leave,” the former drone operator says. “That’s how they confuse us.”

As a result, even when the agency correctly identifies and targets a SIM card belonging to a terror suspect, the phone may actually be carried by someone else, who is then killed in a strike. According to the former drone operator, the geolocation cells at the NSA that run the tracking program – known as Geo Cell –sometimes facilitate strikes without knowing whether the individual in possession of a tracked cell phone or SIM card is in fact the intended target of the strike.

“Once the bomb lands or a night raid happens, you know that phone is there,” he says. “But we don’t know who’s behind it, who’s holding it. It’s of course assumed that the phone belongs to a human being who is nefarious and considered an ‘unlawful enemy combatant.’ This is where it gets very shady.”

The former drone operator also says that he personally participated in drone strikes where the identity of the target was known, but other unknown people nearby were also killed.

“They might have been terrorists,” he says. “Or they could have been family members who have nothing to do with the target’s activities.”

What’s more, he adds, the NSA often locates drone targets by analyzing the activity of a SIM card, rather than the actual content of the calls. Based on his experience, he has come to believe that the drone program amounts to little more than death by unreliable metadata.

“People get hung up that there’s a targeted list of people,” he says. “It’s really like we’re targeting a cell phone. We’re not going after people – we’re going after their phones, in the hopes that the person on the other end of that missile is the bad guy.”

None of this works if the target turns his phone off or exchanges SMS cards often with his colleagues which is routine. It won’t work in much of Yemen, which isn’t on any cell phone network. Because of this, the NSA also tracks people based on their actions on the Internet

In addition to the GILGAMESH system used by JSOC, the CIA uses a similar NSA platform known as SHENANIGANS. The operation—previously undisclosed—utilizes a pod on aircraft that vacuums up massive amounts of data from any wireless routers, computers, smart phones or other electronic devices that are within range.